Every local authority in Wales is exceeding the government's maximum number of surplus places in schools - 10% - according to the schools' watchdog Estyn.
The report published today also claims the number of unfilled places has gone up in the last five years.
Our Education Correspondent Joanna Simpson has been talking to the author of the report.
According to the schools inspectorate there were nearly 100,000 surplus places in Wales in 2011.
Local Authorities have been cited as part of the reason for the increase in empty places saying they have been "reluctant" to make decisions over reorganisation and school closures.
– Ann Keane, Estyn Chief Inspector
Local authorities are responsible for ensuring that there are enough places for all pupils in its schools and that there are no surplus places.
*"This is a difficult task as, currently, we are seeing an increase in the number of primary pupils but a decrease in pupil numbers in secondary schools. *
"However, despite the removal of some surplus places, local authorities have been slow to identify and complete projects which could lead to significant savings. "
Within the report it has been estimated that a saving of £260 for each surplus primary place and £510 for each surplus secondary place could be saved.
The report provides a number of recommendations for the Welsh Government and local authorities, including adopting a standardised method for use at national level to identify the average cost of surplus places and surplus schools; promoting the reduction of surplus places as part of better resource management and carefully monitoring and evaluating all school reorganisation projects.